1. Field of the Invention
The present invention relates to a phosphor having efficient emission at a low voltage, and more particularly, to a SrTiO3:Pr, Al based phosphor applicable for driving displays at a low voltage, which is a kind of oxide phosphor emerging as a very likely substitute for sulfide based phosphors.
2. Description of the Related Art
Field emission displays (FEDs) need a phosphor with high luminescent efficiency to be driven with low voltages of 1 kV or less. An existing sulfide based phosphor applied to FEDs has problems in terms of chemical stability and charge build-up during operation. To avoid these problems, research has been conducted into oxide based phosphors.
Oxide based phosphors have a luminance which is 30 to 40% of that of sulfide based phosphors. The sulfide based phosphor used in FEDs has effective emission at a high voltage (5 to 10 kV). However, in FEDs operated with a driving voltage as low as 1 kV or less, the luminance is lowered due to the problem of charge-build up. For this reason, there is a need for a novel phosphor with high luminescent efficiency at a low voltage, especially for a high-efficiency oxide based phosphor capable of replacing the existing sulfide phosphor.
One kind of oxide based phosphor that has been developed is SrTiO3:Pr phosphor. However, the SiTiO3:Pr phosphor shows low luminance at a low voltage. To improve this problem, U.S. Pat. No. 5,619,098 taught SrTiO3:Pr, Al based phosphors with increased luminance. However, further development of phosphors for FEDs having effective emission and stability at a driving voltage as low as 1 kV or less, is needed.
To solve the above problems, it is an objective of the present invention to provide a SrTiO3:Pr, Al based phosphor having high luminance, applicable to display devices such as field emission displays (FEDs) operating with a voltage as low as 1 kV or less.
The objective of the present invention is achieved by a SrTiO3:Pr, Al based phosphor having effective emission at a low voltage, having the composition of (MeIMeIIMeIII)TiO3. A2O3 obtained by adding MeII to a phosphor having the composition of (MeIMeIII)TiO3. A2O3, where MeI is a metal selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr) and barium (Ba); MeII is a metal of zinc (Zn) or cadmium (Cd), MeIII is a metal selected from the group consisting of praseodymium (Pr), europium (Eu), terbium (Tb), erbium (Er), cerium (Ce) and thulium (Tm), and A is a metal selected from the group consisting of aluminum (Al), gallium (Ga), indium (In) and thallium (Tl).
Preferably, in the above composition of (MeIMeIIMeIII)TiO3. A2O3, MeII is Zn and A. Preferably, MeII is added in an amount of 0.01 to 15 mole %, and at least one flux selected from the group consisting of SrCl2, ZnCl2, Srl2, Znl2 and Cdl2 is used. If the flux is used, the amount of flux may be in the range of 0.5 to 60 mole %. Preferably, in the composition of (MeIMeIIMeIII)TiO3. A2O3, MeIII is added in an amount of 0.05 to 5 mole %, and A is added in an amount of 0.5 to 80 mole %.